[QUOTE=GenoMax;114232]From Bowtie website:
They also say:
'If your computer has more than 3-4 GB of memory and you would like to exploit that fact to make index building faster, use a 64-bit version of the bowtie2-build binary. The 32-bit version of the binary is restricted to using less than 4 GB of memory. If a 64-bit pre-built binary does not yet exist for your platform on the sourceforge download site, you will need to build one from source.'

I thought 64 bit binary, should be able to handle more characters as well; not true?

From Bowtie website:
They also say:
'If your computer has more than 3-4 GB of memory and you would like to exploit that fact to make index building faster, use a 64-bit version of the bowtie2-build binary. The 32-bit version of the binary is restricted to using less than 4 GB of memory. If a 64-bit pre-built binary does not yet exist for your platform on the sourceforge download site, you will need to build one from source.'

I thought 64 bit binary, should be able to handle more characters as well; not true?

That reference is only for being able to use more memory during the index building stage to speed that process up.

Dear Ben,
Why is the last version of Bowtie using the mm9 rather than mm10?
What is better Bowtie or Bowtie2 for alighment of 50 nt HiSeq Illumina ChIP-Seq redas?
I have read that Bowtie is good for short reads up to 100 nt, but Bowtie2 from 50 nt and higher. Still 50 nt reads are on the border for the programms.
If Bowtie2 is used, how to get rid of ununique reads?
Many thanks in advance

Hi Ben,
Sorry to resurrect an old post. I am getting the error Error: Reference sequence has more than 2^32-1 characters!. I know this means I need to split my reference in order to use bowtie2-build but I am wondering about mapping my reads to this reference which has been split. Is it possible to concatenate the split-indexed files and map the reads to this concatenated file or will I have to map the reads to each indexed files separately and write scripts to find which has the best hit.
Thank you
Angela

Reply to thread 'Bowtie, an ultrafast, memory-efficient, open source short read align

Hi Angie,

I think if you use split reference you'll have issues calculating the alignment quality of the best alignment during the merge, it's a bit more complicated than just selecting the best alignment.
You will likely get more accurate alignment qualities if you don't split the reference and instead use an aligner like BWA or Novoalign that can handle genomes >4Gbp.

KR, Colin

Quote:

Originally Posted by angie_red

Hi Ben,
Sorry to resurrect an old post. I am getting the error Error: Reference sequence has more than 2^32-1 characters!. I know this means I need to split my reference in order to use bowtie2-build but I am wondering about mapping my reads to this reference which has been split. Is it possible to concatenate the split-indexed files and map the reads to this concatenated file or will I have to map the reads to each indexed files separately and write scripts to find which has the best hit.
Thank you
Angela

I think if you use split reference you'll have issues calculating the alignment quality of the best alignment during the merge, it's a bit more complicated than just selecting the best alignment.
You will likely get more accurate alignment qualities if you don't split the reference and instead use an aligner like BWA or Novoalign that can handle genomes >4Gbp.

KR, Colin

While using BWA or Novoalign are certainly the better solutions, one can relatively simply recalculate MAPQs from multiple alignment files to different references with bowtie. The bowtie MAPQ score is dependent primarily on the AS:i: and XS:i: score of each read, so you can just rerun the algorithm on that (bowtie MAPQs are more of a vague approximation than you may think). This is the approach I took in bison, where there are multiple parallel alignments of each read to different bisulfite converted genomes.

Agree you can merge Bowtie and calculate a vague alignment quality. Perhaps you can give Angie the formulae for it.

Quote:

Originally Posted by dpryan

While using BWA or Novoalign are certainly the better solutions, one can relatively simply recalculate MAPQs from multiple alignment files to different references with bowtie. The bowtie MAPQ score is dependent primarily on the AS:i: and XS:i: score of each read, so you can just rerun the algorithm on that (bowtie MAPQs are more of a vague approximation than you may think). This is the approach I took in bison, where there are multiple parallel alignments of each read to different bisulfite converted genomes.

Agree you can merge Bowtie and calculate a vague alignment quality. Perhaps you can give Angie the formulae for it.

Inputs are the AS and XS score of the resulting best hit (the XS score may be the AS score of the second best hit, that is the alignment to the other chunk of the reference). scMin is the minimum score for a given read (this is derived from the --score-min option given as input). I have a function to calculate this, but it depends on previously parsing user input and storing things in a struct that's specific to bison (so that function wouldn't be very useful), so I won't paste it below. This is basically a C version of what bowtie2 uses (complete with casting single-precision floats to double precision).

Oh, the config.mode just denotes --end-to-end or --local. You'd need to change that to be a function input rather than relying on a global struct I think the remainder should work, though!

I starting using bowtie today, i wanted to align csfasta + qual file width the bowtie.
I build the reference fasta file width the bowtie-build, after that i try to align the csfasta+qual file to the reference file(s), but i have error massege.
The bowtie-build command:

Hi Ben,
really happy that i can talk with you here because at first when i was working with bowtie2 i asked myself how much you can be clever that created bowtie and how much i am not who cant run bowtie properly...
anyway i have a question about --un option:
if i want to separate mapped and unmapped reads when aligning, which code i should type???
bowtie2 -x [name of the bowtie2-build indicized file containing the rRNA sequence] --un [name of the fastq file which will contain the UNMAPPED reads] -U [name of the fastq file containing the reads] -S [name of the .sam file that will contain the MAPPED and UNMAPPED reads]
I could not understand about --un option because i don't know which i should type instead of [name of the fastq file which will contain the UNMAPPED reads]